case sensitive aggregation in mongodb using mongoose

Question

Hi all I am trying to do a auto populate dropdown search using mongoose and mongodb. I have written a aggregate query which works case insensitive was like if there are 2 datas like "brand" and "Brand" if i give "brand" it gives output for both "brand" and "Brand". Below is my aggregate query

var aggregate = model.aggregate([
  {
    $match:{
     deleted: false
   }
  },
  {
    $group: {
      _id: $brand,
      Id: { $first: '$_id' },
      count: { $sum: 1 }
    }
  },
  {
    $project: {
      _id: '$Id',
      name: '$_id',
      count: '$count',
      insensitive: { $toLower: '$_id' }
    }
  },
  { $sort: { insensitive: 1 } },
  {
    $project: {
      _id: '$_id',
      name: '$name',
      count: '$count'
    }
  },

] );

My use case here is that i should display only the data specified like if i give brand it should display only "brand" and not "Brand". Kindly help me